Posted on March 19, 2013 at 18:45 https://community.st.com/0D50X00009XkbNMSAZ
The CRC processes 32-bits at a time, applying them in a small-endian fashion. It is not performed byte wise in the manner most online testers use.It can be computed on the STM32 or x86 PC with the following code. The nibble table method is a trade off between speed and space.DWORD Crc32(DWORD Crc, DWORD Data){int i;Crc = Crc ^ Data;for(i=0; i<32; i++)if (Crc & 0x80000000)Crc = (Crc << 1) ^ 0x04C11DB7; // Polynomial used in STM32elseCrc = (Crc << 1);return(Crc);}DWORD Crc32Fast(DWORD Crc, DWORD Data){static const DWORD CrcTable[16] = { // Nibble lookup table for 0x04C11DB7 polynomial0x00000000,0x04C11DB7,0x09823B6E,0x0D4326D9,0x130476DC,0x17C56B6B,0x1A864DB2,0x1E475005,0x2608EDB8,0x22C9F00F,0x2F8AD6D6,0x2B4BCB61,0x350C9B64,0x31CD86D3,0x3C8EA00A,0x384FBDBD };Crc= Crc ^ Data; // Apply all 32-bits// Process 32-bits, 4 at a time, or 8 roundsCrc = (Crc << 4) ^ CrcTable[Crc >> 28]; // Assumes 32-bit reg, masking index to 4-bitsCrc = (Crc << 4) ^ CrcTable[Crc >> 28]; // 0x04C11DB7 Polynomial used in STM32Crc = (Crc << 4) ^ CrcTable[Crc >> 28];Crc = (Crc << 4) ^ CrcTable[Crc >> 28];Crc = (Crc << 4) ^ CrcTable[Crc >> 28];Crc = (Crc << 4) ^ CrcTable[Crc >> 28];Crc = (Crc << 4) ^ CrcTable[Crc >> 28];Crc = (Crc << 4) ^ CrcTable[Crc >> 28];return(Crc);}{printf('%08X',Crc32(0xFFFFFFFF, 0x12345678)); // 0xDF8A8A2Bprintf('%08X',Crc32Fast(0xFFFFFFFF, 0x12345678)); // 0xDF8A8A2B}
Edit: Fixed DEAD LINK, original post from March 19, 2013
